kernel/git/stable/linux.git/security/apparmor/policy.c, branch master

apparmor: fix deadlock in complain-mode change_hat

2026-08-16T06:39:38+00:00

The use of change_hat when in complain mode can cause a deadlock when the hat doesn't exist and a new learning profile is created for the missing profile. This is because change_hat() has taken the lock to search the hat list and creating the new learning profile needs to take the lock to add it to the list. From the bug report: Originally found in 7.0.0 in LTS ubuntu 26.04 with pam_apparmor + su in complain mode set to change hats. Then verified in newest available vanilla kernel I've compiled to see if still present: 7.2-rc7 vanilla -> affected checked also some other kernels: 6.18.44 vanilla -> affected 6.12.95 with debian patches -> unaffected On systems without bug (for example 6.12.95 debian) it just prints: aa_change_hat rc=0 On systems with bug, the executable always hangs, prints nothing and becomes unkillable. (And once stuck this way, it will cause any further hat changes to also cause the changing process to get stuck) Then in syslog you can find hint about cause: kernel: INFO: task hat:3409 blocked for more than 483 seconds. kernel: Not tainted 7.2.0-rc7 #1 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kernel: task:hat state:D stack:0 pid:3409 tgid:3409 ppid:2605 task_flags:0x400000 flags:0x00080800 kernel: Call Trace: kernel: kernel: __schedule+0x48f/0xfe0 kernel: schedule+0x27/0xa0 kernel: schedule_preempt_disabled+0x15/0x30 kernel: __mutex_lock.constprop.0+0x569/0xa10 kernel: aa_new_learning_profile+0x15f/0x210 kernel: build_change_hat+0x19f/0x3b0 kernel: change_hat.isra.0+0x5dd/0xd60 kernel: aa_change_hat+0x2f3/0x710 kernel: aa_setprocattr_changehat+0x121/0x1f0 kernel: do_setattr+0x28c/0x340 kernel: apparmor_setselfattr+0x20/0x50 kernel: security_setselfattr+0xf6/0x110 kernel: __x64_sys_lsm_set_self_attr+0x53/0x90 kernel: do_syscall_64+0xdd/0x5e0 kernel: ? __mod_memcg_lruvec_state+0xfd/0x260 kernel: ? lruvec_stat_mod_folio+0x8d/0xd0 kernel: ? __folio_mod_stat+0x2d/0x90 kernel: ? map_anon_folio_pte_nopf+0xd1/0x1f0 kernel: ? do_anonymous_page+0x184/0xa10 kernel: ? __handle_mm_fault+0x805/0x870 kernel: ? count_memcg_events+0xef/0x230 kernel: ? handle_mm_fault+0x1f0/0x2f0 kernel: ? do_user_addr_fault+0x2bb/0x7b0 kernel: ? do_syscall_64+0x94/0x5e0 kernel: ? exc_page_fault+0x75/0x160 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e kernel: RIP: 0033:0x7f815e134c8d kernel: RSP: 002b:00007fff6df94ea8 EFLAGS: 00000246 ORIG_RAX: 00000000000001cc kernel: RAX: ffffffffffffffda RBX: 0000556d8c81d040 RCX: 00007f815e134c8d kernel: RDX: 0000000000000046 RSI: 0000556d8c81d040 RDI: 0000000000000064 kernel: RBP: 00007fff6df94ef0 R08: 00007f815e212ac8 R09: 000000000000000c kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 0000556d8c81d010 kernel: R13: 0000000000000026 R14: 0000000000000046 R15: 0000000000000064 kernel: kernel: INFO: task hat:3409 is blocked on a mutex likely owned by task hat:3409. To fix the issue, lift the locking out of the core of aa_new_learning_profile(), introduce a wrapper function that takes the lock where needed, and have build_change_hat() call the core function that no longer takes the lock. In addition fix 4 other issues introduced by commit 32e92764d6f8d ("apparmor: grab ns lock and refresh when looking up changehat child profiles") - aa_get_profile_rcu() was replaced-by: aa_get_profile without the accompanying rcu_dereference_protected() - an extra aa_get_label(label) was introduced at the start of change_hat() without an accompanying aa_put_label() causing a reference count leak. - a reference count leak was introduced in the label_is_stale(label) case, where the newest profile would be leaked instead of the label passed to the function. - a potential UAF when the lookup walks up the tree with new_ns != ns the new label reference is put, and then used for the next lookup. The mutex_lock, will block replacement, and removal in the locked ns. However there are two cases where putting the reference can result in the label being freed even with the lock held. 1. the label does not have a list reference (possible for temporary or special profiles) in which case the put can trigger the cleanup. 2. the new label reference is in a different namespace, which does not have a lock held on it. This extends case 1 to also include replacement, and removal that could be occurring in the namespace new is in. Reported-by: Martin Petricek Link: https://lists.ubuntu.com/archives/apparmor/2026-August/014907.html Fixes: 32e92764d6f8d ("apparmor: grab ns lock and refresh when looking up changehat child profiles") Signed-off-by: John Johansen

apparmor: Initial support for compressed policies

2026-06-29T17:27:02+00:00

This patch allows policies to be compressed in userspace and be sent to the kernel through the existing ".load" and ".replace" kernel interfaces. The benefits of this approach are: - Save kernel time when loading policies - Allow userspace to provide a higher level of compression than the one provided by the kernel (ZSTD_CLEVEL_DEFAULT), thus saving space. - Allow small embedded systems to only store the compressed version of policies in userspace, saving memory. Userspace-compressed policies improve system time by up to ~30% for big profiles. Signed-off-by: Maxime Bélair Signed-off-by: John Johansen

apparmor: fix net.h and policy.h circular include pattern

2026-06-29T17:26:21+00:00

While the #ifdef guards prevent the circular include from blowing up, policy.h does not actually need anything from net.h. Remove, that include and instead include net.h in the other files that need it. Signed-off-by: Ryan Lee Signed-off-by: John Johansen

apparmor: fix label can not be immediately before a declaration

2026-06-15T01:22:35+00:00

Fix error reported by kernel test robot security/apparmor/policy.c:1381:2: error: a label can only be part of a statement and a declaration is not a statement All errors (new ones prefixed by >>): security/apparmor/policy.c: In function 'aa_replace_profiles': >> security/apparmor/policy.c:1381:2: error: a label can only be part of a statement and a declaration is not a statement ssize_t udata_sz = udata->size; ^~~~~ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202606150525.npax8WiH-lkp@intel.com/ Fixes: 7b42f95813dc9 ("apparmor: fix potential UAF in aa_replace_profiles") Signed-off-by: John Johansen

apparmor: fix use-after-free in rawdata dedup loop

2026-06-14T03:20:13+00:00

aa_replace_profiles() walks ns->rawdata_list to dedup the incoming policy blob against entries already attached to existing profiles. Per the kernel-doc on struct aa_loaddata, list membership does not hold a reference: profiles hold pcount, and when the last pcount drops, do_ploaddata_rmfs() is queued on a workqueue that takes ns->lock and removes the entry. Between dropping the last pcount and the workqueue running, an entry remains on the list with pcount == 0. aa_get_profile_loaddata() is an unconditional kref_get() on pcount, so when the dedup loop hits such an entry, refcount hardening reports refcount_t: addition on 0; use-after-free. inside aa_replace_profiles(), and the poisoned counter then trips "saturated" and "underflow" warnings on the subsequent uses of the same loaddata. Before commit a0b7091c4de4 ("apparmor: fix race on rawdata dereference") the dedup path used a get_unless_zero-style helper on a single counter, so the existing "if (tmp)" guard was meaningful. The split-refcount refactor introduced aa_get_profile_loaddata(), which has plain kref_get() semantics, and the guard quietly became a no-op. Introduce aa_get_profile_loaddata_not0(), matching the existing _not0 convention used by aa_get_profile_not0(), and use it for the rawdata_list dedup lookup so dying entries are skipped. Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu 24.04 + stress-ng 0.17.06: stress-ng --apparmor 1 --klog-check --timeout 60s Without this patch the three refcount_t warnings fire within a few seconds. With it the same 60 s run is clean. Coverage is a smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN and CONFIG_PROVE_LOCKING would be welcome from anyone with the cycles. Fixes: a0b7091c4de4 ("apparmor: fix race on rawdata dereference") Reported-by: Colin Ian King Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221513 Cc: stable@vger.kernel.org Signed-off-by: Ruslan Valiyev Signed-off-by: John Johansen

apparmor: remove or add symlinks to rawdata according to export_binary

2026-06-14T03:14:07+00:00

When the export_binary parameter is set, then rawdata is available and there should be a symbolic link for the rawdata in the profile directory in apparmorfs. If the parameter is unset, then the symlinks should not exist. The issue arises when changing the value of export_binary on runtime and replacing profiles. If export_binary was set when the profile was originally loaded, then changed to 0 and the profile was reloaded, then the symbolic links would still exist but would return ENOENT because the rawdata no longer exists. On the opposite side, if export_binary was unset when the profile was originally loaded, then changed to 1 and the profile was reloaded, then the symbolic links would not exist, even though the rawdata does. Fixes: d61c57fde8191 ("apparmor: make export of raw binary profile to userspace optional") Signed-off-by: Georgia Garcia Signed-off-by: John Johansen

apparmor: fix potential UAF in aa_replace_profiles

2026-06-14T03:14:07+00:00

The function aa_replace_profiles was accessing udata->size after calling aa_put_loaddata(udata), causing a potential UAF. Fixed this by saving the size to a local variable before dropping the reference. Fixes: 5ac8c355ae001 ("apparmor: allow introspecting the loaded policy pre internal transform") Reviewed-by: Georgia Garcia Signed-off-by: Maxime Bélair Signed-off-by: John Johansen

apparmor: free rawdata as soon as possible

2026-06-14T03:14:07+00:00

profiles can be pinned by file and other references, and can live long after they have been replaced/removed. The rawdata however is no longer needed, and can be freed earlier than the rest of the profile. Reviewed-by: Georgia Garcia Signed-off-by: John Johansen

apparmor: fix race on rawdata dereference

2026-03-09T23:05:44+00:00

There is a race condition that leads to a use-after-free situation: because the rawdata inodes are not refcounted, an attacker can start open()ing one of the rawdata files, and at the same time remove the last reference to this rawdata (by removing the corresponding profile, for example), which frees its struct aa_loaddata; as a result, when seq_rawdata_open() is reached, i_private is a dangling pointer and freed memory is accessed. The rawdata inodes weren't refcounted to avoid a circular refcount and were supposed to be held by the profile rawdata reference. However during profile removal there is a window where the vfs and profile destruction race, resulting in the use after free. Fix this by moving to a double refcount scheme. Where the profile refcount on rawdata is used to break the circular dependency. Allowing for freeing of the rawdata once all inode references to the rawdata are put. Fixes: 5d5182cae401 ("apparmor: move to per loaddata files, instead of replicating in profiles") Reported-by: Qualys Security Advisory Reviewed-by: Georgia Garcia Reviewed-by: Maxime Bélair Reviewed-by: Cengiz Can Tested-by: Salvatore Bonaccorso Signed-off-by: John Johansen

apparmor: fix unprivileged local user can do privileged policy management

2026-03-09T23:05:43+00:00

An unprivileged local user can load, replace, and remove profiles by opening the apparmorfs interfaces, via a confused deputy attack, by passing the opened fd to a privileged process, and getting the privileged process to write to the interface. This does require a privileged target that can be manipulated to do the write for the unprivileged process, but once such access is achieved full policy management is possible and all the possible implications that implies: removing confinement, DoS of system or target applications by denying all execution, by-passing the unprivileged user namespace restriction, to exploiting kernel bugs for a local privilege escalation. The policy management interface can not have its permissions simply changed from 0666 to 0600 because non-root processes need to be able to load policy to different policy namespaces. Instead ensure the task writing the interface has privileges that are a subset of the task that opened the interface. This is already done via policy for confined processes, but unconfined can delegate access to the opened fd, by-passing the usual policy check. Fixes: b7fd2c0340eac ("apparmor: add per policy ns .load, .replace, .remove interface files") Reported-by: Qualys Security Advisory Tested-by: Salvatore Bonaccorso Reviewed-by: Georgia Garcia Reviewed-by: Cengiz Can Signed-off-by: John Johansen